1. Field of the Invention
The present invention relates to a tightening string for an endoscope, an outer cover securing method, a flexible tube for an endoscope, and an endoscope, and more specifically relates to a tightening string for use in an endoscope for securing an outer cover of a flexible tube of the endoscope onto a core member of the flexible tube disposed inside the outer cover, an outer cover securing method using the tightening string, a flexible tube for an endoscope equipped with the thus secured outer cover, and an endoscope equipped with the flexible tube.
2. Description of the Related Art
In the medical fields, an endoscope is used for examining and diagnosing a gastrointestinal tract or the like of a patient.
Such an endoscope includes an insertion section flexible tube which is to be inserted into a body cavity of a patient, an operating section for performing operations of the insertion section flexible tube, a connecting section flexible tube connected to the operating section, and a light source plug provided on the tip end of the connecting section flexible tube.
The insertion section flexible tube (hereinafter, simply referred to as “flexible tube”) has an elongated flexible tubular portion and a bendable portion coupled to the tip end of the flexible tubular portion in a bendable manner. The body cavity can be observed in all directions by rotating the flexible tube and, at the same time, bending the bendable portion of the flexible tube appropriately.
In general, the flexible tubular portion and the bendable portion are respectively comprised of a core member and an outer cover having flexibility and covering the core member. In such an endoscope, the flexible tubular portion and the bendable portion are coupled together in the following manner (for example, see JP-A No. 5-277061).
First, the core members of the flexible tubular portion and the bendable portion are joined together at their end portions, after which the joined part is covered with an outer cover of the bendable portion, and then the end of an outer cover of the flexible tube is brought into contact with the end of the outer cover of the bendable portion.
Then, the outer cover of the flexible tubular portion and the outer cover of the bendable portion are respectively tightened by a string at the opposite sides of the boundary section therebetween, and then an adhesive agent is applied over the string.
By applying the adhesive agent over the tightening string in this manner, the string is secured to the outer cover of the flexible tube and the outer cover of the bendable portion.
In the meantime, an endoscope is subject to cleansing, disinfecting and sterilizing every time upon its use. From the view point of improving safety, stronger treatment agents and methods have been employed in recent years in the process of sterilization.
However, if the strong sterilization treatment is carried out for the endoscope, it causes a problem in that the adhesive agent becomes deteriorated and this causes a brittle fracture in the hardened adhesive or a reduction of bonding strength, thereby loosening the string, which results in decrease in the liquid-tightness at the joining section. In the event that such a problem occurs, a liquid such as a disinfecting liquid or the like may be infiltrated into the inside of the endoscope through the joining section. This involves a risk that the endoscope is out of order.
Further, depending on the property of the string used, there is a case that the outer cover is damaged. The damaged outer cover causes a problem in that the liquid-tightness of the flexible tubular portion and the bendable portion is lowered, and this also involves a risk that the endoscope fails to operate properly.
Furthermore, in order to secure the outer cover to the core member more firmly with suppressing the burden to a patient to which an endoscope is to be inserted as lower as possible, there is a demand that a string which is more suitable for a tightening string for an endoscope should be developed.